DEFOLIATION LEVELS AT VEGETATIVE AND REPRODUCTIVE STAGES OF SOYBEAN CULTIVARS WITH DIFFERENT RELATIVE MATURITY GROUPS

DURLI, MURILO MIGUEL; SANGOI, LUIS; SOUZA, CLOVIS ARRUDA; LEOLATO, LUCIELI SANTINI; TUREK, THAIS LEMOS; KUNESKI, HUGO FRANCOIS

doi:10.1590/1983-21252020v33n213rc

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Agronomy • Rev. Caatinga 33 (2) • Apr-Jun 2020 • https://doi.org/10.1590/1983-21252020v33n213rc copy

DEFOLIATION LEVELS AT VEGETATIVE AND REPRODUCTIVE STAGES OF SOYBEAN CULTIVARS WITH DIFFERENT RELATIVE MATURITY GROUPS

NÍVEIS DE DESFOLHA NAS FASES VEGETATIVA E REPRODUTIVA DE CULTIVARES DE SOJA COM DIFERENTES GRUPOS DE MATURAÇÃO RELATIVA

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Soybean tolerance to defoliation may be affected by relative maturity group (RMG) of the cultivar. For this reason, this study was carried out to evaluate the effects of artificial defoliation at vegetative and reproductive stages on the agronomic performance of soybean cultivars with different RMG. Two experiments were carried out in greenhouse conditions in Lages, Santa Catarina State, Brazil. Defoliation was carried out at V6 in the first experiment and at R3 in the second experiment. Three cultivars with contrasting RMG were used: BMX Veloz (RMG of 5.0, indeterminate growth habit), NA 5909 (RMG of 5.9, indeterminate growth habit), and TMG 7262 (RMG of 6.2, semi-determinate growth habit). Each cultivar was submitted to five defoliation levels: 0.0, 16.6, 33.3, 50.0, and 66.6%. Leaf expansion after defoliation, grain yield and its components were determined. The BMX Veloz showed lower leaf expansion capacity and lower grain yield when compared to the other cultivars when defoliated at V6. Grain yield of the three cultivars only showed significant decreases with defoliation levels higher than 16.6% at R3. The cultivar BMX Veloz is less tolerant to defoliation during the vegetative stage when compared to the cultivars NA 5909 and TMG 7262. Cultivar maturity group does not interfere with soybean tolerance to defoliation at the reproductive stage in greenhouse conditions.

Keywords:
Glycine max L; Merril; Leaf area; Source-sink relationship; Yield

Source of Variation	G. L.	LA R2 (def in V6 and R5 (def in R3)	Leaf expansion (V6 to R2) (R2 to R5)	Grain yield	1000 grain weight	Number of pods per plant	Number of grains per pod
	Experiment with defoliation at V6
Cultivar (C)	2	22.0756^ significant at the 1% probability level (p<0.01).	16.21^ significant at the 1% probability level (p<0.01).	164.64^ significant at the 1% probability level (p<0.01).	79.17^ significant at the 1% probability level (p<0.01).	52.57^ significant at the 1% probability level (p<0.01).	0.40 ns
Defoliation (D)	4	10.63^ significant at the 1% probability level (p<0.01).	0.12 ns	35.31^ significant at the 1% probability level (p<0.01).	75.48^ significant at the 1% probability level (p<0.01).	3.28^* * significant at the 5% probability level (p<0.05).	1.49 ns
C x D	8	0.82 ns	0.79 ns	3.41^ significant at the 1% probability level (p<0.01).	5.89^ significant at the 1% probability level (p<0.01).	1.28 ns	0.23 ns
Blocks	2	1.38 ns	0.18 ns	2.79 ns	0.88 ns	2.64 ns	0.65 ns
Error	28
Total	44
	Experiment with defoliation at R3
Cultivar (C)	2	213.21^ significant at the 1% probability level (p<0.01).	114.52^ significant at the 1% probability level (p<0.01).	70.93^ significant at the 1% probability level (p<0.01).	66.16^ significant at the 1% probability level (p<0.01).	63.23^ significant at the 1% probability level (p<0.01).	2.61 ns
Defoliation (D)	4	9168^ significant at the 1% probability level (p<0.01).	5.85^ significant at the 1% probability level (p<0.01).	39.29^ significant at the 1% probability level (p<0.01).	61.62^ significant at the 1% probability level (p<0.01).	18.54^ significant at the 1% probability level (p<0.01).	0.34 ns
C x D	8	8.31^ significant at the 1% probability level (p<0.01).	2.05 ns	1.50 ns	2.17 ns	4.01^ significant at the 1% probability level (p<0.01).	0.82 ns
Blocks	2	9.51^ significant at the 1% probability level (p<0.01).	0.43 ns	0.52 ns	1.11 ns	0.96 ns	2.73 ns
Error	28
Total	44

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Defoliation	Cultivar
(%)	BMX Veloz	A 5909	TMG 7262	Average	CV%
Leaf expansion between V6 and R2 (m²) with defoliation at V6
0.0	0.104	0.110	0.156	0.123 ns
16.6	0.123	0.112	0.139	0.124
33.3	0.114	0.110	0.140	0.121	14.55
50.0	0.126	0.113	0.141	0.127
66.6	0.102	0.116	0.152	0.123
Average	0.110 b	0.112 b	0.146 a
Leaf expansion between R3 and R5 (m²) with defoliation at R3
0,0	0.146	0.059	0.050	0.085 b
16.6	0.116	0.054	0.039	0.069 c
33.3	0.131	0.064	0.031	0.075 bc	19.27
50.0	0.135	0.084	0.080	0.099 a
66.6	0.161	0.057	0.074	0.097 a
Average	0.138 a	0.063 b	0.055 b